In the field of integrated circuits including, in particular, semiconductor devices, isolation structures are commonly used for defining active regions in semiconductor substrates and for insulating adjacent functional units from each other. For example, according to the so-called shallow trench isolation (STI) technology, a shallow isolation trench filled with an insulating material is formed at the surface of a semiconductor substrate. Moreover, according to the deep trench isolation (DTI) technology deep isolation trenches filled with an insulating material are formed in the semiconductor material. For example, a conductive material may be disposed in these deep isolation trenches, the conductive material being insulated from the semiconductor material by the insulating material. The conductive material in the deep isolation trenches accomplishes a contact to an underlying buried layer, or further shields electrical fields. In order to provide an effective isolation even in case of high voltages, improvements of existing deep trench isolation technology are searched for. Accordingly, it would be desirable to provide integrated circuits comprising trenches which can withstand increasing higher voltages.